In January of 1942, as the U.S was entering World War II, a Pennsylvania dentist (and friend of Eleanor Roosevelt) named Lytle Adams submitted the design of a new weapon to the White House, suggesting that it could be effective against the Japanese. Adams' creation was a bomb that would drop over 800 hibernating bats – to each of which was attached a small incendiary device… as the bomb descended from a high-altitude drop, the bats would awaken, disperse, and nest in structures – which in Japan at the time were largely made of bamboo, paper, and other highly-flammable material. Later in the day the incendiaries would go off, starting fires across a wide area. Adams estimated that 100 bombs might start as many a 1,000,000 fires.
The U.S. military developed the "Bat Bomb"; and while the yields were never quite what Adams predicted, they were impressive enough to drive investment of an estimated $2 million. The project was abandoned only when it became clear that the Manhattan Project would finish before the Bat Bomb was ready.
(More about bats and bombs on Boing Boing)